CP Violation in the Semileptonic B_{l4} (B^\pm -> pi^+ \pi^- l^\pm \nu) Decays

TL;DR

This paper investigates direct CP violations in B_{l4} decays within the Standard Model and its extensions, calculating asymmetries and assessing their measurability with current and future B-meson datasets.

Contribution

It provides the first detailed calculation of CP asymmetries in B_{l4} decays considering both SM and extended models with complex couplings.

Findings

Optimal asymmetry measurable with about 10^9 B-mesons in SM

Extended models allow measurement with 10^3 to 10^7 B-mesons

CP violation effects depend on interference of intermediate resonances

Abstract

Direct CP violations in $B_{l4}$ decays ($B^\pm \to \pi^+\pi^- l^\pm {\nu}_l$) are investigated within the Standard Model (SM) and also in its extensions. In the decay processes, we include various excited states as intermediate states decaying to the final hadrons, $\pi^+ + \pi^-$. The CP violation within the SM is induced by the interferences between intermediate resonances with different quark flavors. As extensions of the SM, we consider CP violations implemented through complex scalar-fermion couplings in the multi-Higgs doublet model and the scalar-leptoquark models. We calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry can be measured at $1\sigma$ level with about $10^9$ $B$-meson pairs in the SM case and $10^3$--$10^7$ pairs in the extended model case, for maximally-allowed values of CP-odd parameters in each case.